In the luminaire art it is customary to provide a luminaire housing body in which lamp means may be supported and connected to a power source. A cable member is utilized to connect the lamp means with the power source and includes electrical conductor wires contained in an outer insulating jacket. In such equipment, there are many instances where the interior components of the luminaire body must be held sealed from contact with water and where the electrical components must be protected against strain and pulling forces exerted through the cable either at the point of entry of the cable in the housing body or at the point of connection with the power source.
This is especially true of luminaire apparatus of the cap lamp class wherein a headpiece is carried on a cap member such as, for example, a miner's cap or "hard hat". In such case, the power source is a battery which may be subject to periodic recharging. Moving a battery and its attached cable and headpiece into and out of charging apparatus can exert strain, excessive flexing and pulling forces of substantial intensity particularly where a miner may have a propensity for lifting the battery by means of the cable member. Difficulty may be experienced in sealing a headpiece against water because of the possibility that a vacuum will occur in the headpiece when it is turned off and is no longer subject to internal heating from the bulb.
Various proposals have been made to provide luminaire apparatus in which adequate water seals are realized. Other proposals have sought to combine sealing means with protection against strain and pulling forces exerted through a cable member.
For example, proposals of this nature are disclosed in U.S. Pat. Nos. 13,661,557; 1,757,888; 2,611,073; 2,907,871; 2,794,114; 2,947,853; 3,334,223.
In none of these patented devices has there been provided adequate sealing which can be practically combined with luminaire apparatus of the class referred to nor has there been disclosed any practical and efficient means of protecting electrical conductor elements from straining, flexing and pulling forces exerted through a cable jacket in which the conductor elements are contained.